The technology of High Definition Multimedia Interface, which is abbreviated as HDMI, may be adopted to provide a high bandwidth and transmit digital video signals and audio signals simultaneously without loss. Therefore, HDMI has been widely applied to various consumptive electronic devices and has been developed to a current specification version of HDMI 2.0.
The technology of High-bandwidth Digital Content Protection, which is abbreviated as HDCP, is proposed for protecting high definition signals transmitted with HDMI from being illegally recorded. HDCP is adopted to encrypt HDMI signals. In a case that a user illegally reproduces the encrypted content, the reproduced video file will have a reduced quality due to the use of HDCP, and thereby high definition multimedia content in the video file is protected. HDCP has been developed to a current specification version of HDCP 2.2.
However, in encrypting signals of HDMI 2.0, it is required according to HDCP 2.2 that a clock of a digital circuit operates at a frequency of 600 MHz. In order to cause a clock of a digital circuit to operate at a frequency of 600 as required by the structure and algorithm of HDMI 2.0 and HDCP 2.2, the digital circuit has to be taped out with a deep submicron process, resulting in a high cost, complicated implementation and difficult development.